Spacecraft Overview    ===================      The design of Mariner Mars 1971 spacecraft was similar to that      of Mariner Mars 1969, but incorporated changes required by the      different payload complements, changes required to increase      reliability for a nominal transit cruise and a 90-day-in-orbit      operational lifetime, and changes required for the spacecraft to      accomplish the mission.  The spacecraft weighed approximately      2238 lbs; of this weight 1050 lb was propellant required to      correct the transit trajectory and to perform the orbital      insertion and 152 lb.  which constituted the science payload.      The spacecraft configuration consisted of four solar panels, a      low-gain antenna, a maneuver engine, a Canopus sensor, two      propulsion tanks, two propulsion pressurization tanks,      temperature control louvers, four acquisition sun sensors, a      cruise sun sensor, a medium-gain antenna, a high-gain antenna      and a scan platform.    Platform Descriptions    =====================      The scan platform was an articulating instrument mount providing      a pointing selection capability of 215 degrees in azimuth and 69      degrees in elevation.  The scan platform contained the following      instruments; the infrared radiometer, the wide-angle TV, the      ultraviolet spectrometer, the narrow- angle TV and the IR      Interferometer spectrometer.